The invention relates to a device used by professionals within the optical and ophthalmic industry to heat dyes to a specific temperature to color plastic lenses.
Within the optical lens manufacturing industry, it has been a widespread practice to color plastic lenses after manufacture in accordance with the customer's preference. Numerous devices have been used for this purpose. The most common is a type that utilizes a double tank system. The outer tank is heated electrically and contains a heat transfer medium. The inner tanks, which contain dye, are immersed in the heat transfer medium which indirectly heats each tank of dye. The dyes used in this process are prone to crystallization, decomposition and sediment formation. The double tank system reduces this tendency. Optical dyes only diffuse well into plastic lenses within a narrow temperature range (200-210.degree. F.). The temperature of double tank system has proven hard to control precisely.